This story was originally produced by WBUR. NHPR is republishing it in partnership with the New England News Collaborative.
As New England bakes during the first heat wave of the summer, electricity use is surging. The power grid has so far been able to meet the demand, thanks in part to an assist from the sun.
Around the region, thousands of solar panels on rooftops, over parking lots and along the sides of roads are converting sunlight into electricity and helping relieve stress on the grid.
This small but mighty source of power isn’t controlled by the organization that operates the power grid, earning it the name “behind-the-meter” solar. The electricity it generates is typically used in the homes and businesses where the panels are located.
Historically, behind-the-meter solar has contributed limited amounts of electricity in New England. But over the last 15 years, it’s taken off. Taken together, these small solar arrays now have the ability to generate about 5,000 megawatts of power for the region — more than all of New England’s nuclear power plants combined. By 2045, ISO New England, the regional grid operator, expects that capacity to more than double.
Behind-the-meter solar can produce a meaningful amount of electricity whenever the sun is shinning, but it’s particularly helpful at times of high energy demand, like afternoons during a heat wave.
“ On a hot summer day, everybody is using electricity, and we need every resource we can get,” said Jeremy McDiarmid, managing director of Advanced Energy United, a clean energy industry association group. “Behind-the-meter solar plays a pivotal role in keeping the lights on.”
During this week’s heat wave, ISO New England predicts the region will experience days with some of the highest energy demand of the summer. On Monday, electricity use peaked around 7 p.m. with consumers using about 24,380 megawatts of power. That’s nearly twice as much as last Monday, when temperatures were cooler, and use peaked at about 14,400 megawatts. (When measuring official “peak” demand, the ISO does not count behind-the-meter solar.)
On Tuesday, forecasted to be the hottest day of the week, ISO New England predicts electricity use will peak slightly higher, at at 25,800 megawatts.
“What we’re expecting this week is the highest [demand] we’ve seen this year,” said Matt Kakley, a spokesperson for ISO New England. “But it is in line with what we expected heading into the summer, and we expect to have the resources we need to meet consumer demand for electricity.”
In other words, the region’s power plants and renewable energy resources, like wind and solar farms, should have no trouble keeping up with demand.
ISO New England can’t monitor behind-the-meter solar production like it does the region’s utility-scale solar farms, but it uses computers to model their output. These systems have become sophisticated enough to account for small weather variations, like isolated patches of clouds, that affect electricity generation.
Kakley said behind-the-meter solar is factored into ISO New England’s decisions about what other sources of power they may need to turn on. And with a string of hot and sunny days like this week, “we’re counting on it showing up,” he added.
On Monday at 3 p.m., as temperatures in Greater Boston hovered in the low-to-mid 90s and the sun was shinning, behind-the-meter solar met a substantial part of the region’s electricity needs. According to ISO New England data, households and businesses across New England used more than 26,000 megawatts of power. And 18% of that — about 4,700 megawatts — was met by behind-the-meter solar.
“Behind-the-meter solar is already benefiting New Englanders by shaving summertime peaks” in energy demand, said Joe LaRusso, manager of the Clean Grid Program at the Acadia Center, a nonprofit focused on clean energy research and advocacy.
Most of New England’s electricity comes from burning natural gas and nuclear power. But when energy use spikes, the grid operator turns to “peaker plants” to help meet the demand. These tend to be older, more polluting facilities that are expensive to operate; in New England, many of them burn oil or coal.
“Without behind-the-meter solar, New England would have needed to burn that much more coal and oil to balance the supply of electricity with customer demand.” LaRusso said. “It reduces the cost of meeting the peak, and reduces system-wide emissions that contain not only carbon, but other pollutants including airborne particles that can cause respiratory illnesses.”
As evening fell on Monday, solar production dropped off, and oil production increased. By 7 p.m., oil and coal accounted for about 1,900 megawatts of power on the grid. In the future, LaRusso said, as more behind-the-meter solar is installed, and batteries to store excess power become more common, he hopes the region can rely even less on peaker plants to get through heat waves.
Beyond providing a key source of emissions-free power, advocates argue that behind-the-meter solar can help reduce utility bills in the long run — even for those who don’t have panels on their roofs. The electric grid, with all of its expensive transmission lines and substations, must be built to accommodate peak demand. If peak demand is lower, they say, ratepayers will be on the hook for less of that expensive infrastructure.
“By generating power close to where it is used, rooftop solar reduces strain on the grid and the need for costly transmission upgrades,” said Sean Gallagher, senior vice president of policy for the Solar Energy Industries Association. “And that means fewer power outages and lower energy prices for everyone.”
This article was originally published on WBUR.org.
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